Greetings fellow SkyWatchers! The week starts off rather special as observers in Alaska get the opportunity to watch the Moon occult Venus and more. The return of the Moon might mean the loss of early evening deep sky studies, but we'll still enjoy lunar features and the timeless dance of its orbital track. Take advantage of every clear night as the Perseid meteor shower gears up for its annual peak on Thursday. Keep your eyes on the skies, because...

Here's what's up!

The Mars Exploration Rovers have unquestionably been one of NASA's most exciting and successful missions to date. The projects scientific principal investigator, Dr. Steve Squyres of Cornell University has written a candid and fascinating new book about the mission. Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet offers an inside look at the journeys the rovers have taken; not only their captivating treks across Mars, but the surprisingly circuitous and difficult route they took from inception to development and launch.

If humans are going to live on Mars, we're going to need to learn how to grow plants in the planet's thin atmosphere, poor soil, severe cold, and total lack of water. This environment will put plants into a severe state of stress and shut down their metabolism, but NASA scientists think they've got strategies to help them cope. By introducing genes from extremophile microbes that can withstand severe changes in environment, scientists are hoping to modify plants so they won't shut down their metabolism in response to stress.

The space shuttle Discovery's landing has been pushed back to Tuesday because of low clouds above Florida's Cape Canaveral on Monday. All three primary landing sites will be activated on Tuesday, so the shuttle can potentially land at Cape Canaveral, Edwards Air Force Base in California, or White Sands Space Harbor in New Mexico. Weather forecasters are expecting similar weather in Florida for Tuesday, so it's likely Discovery will have to use an alternative site. The first landing attempt will be at 0907 UTC (5:07 am EDT).

NASA's Mars Reconnaissance Orbiter (MRO) is set to launch in just a couple of days - its launch window opens up on Wednesday, August 10 at 1153 UTC (7:53 am EDT). If all goes well, the spacecraft will blast off on top of an Atlas V-401 rocket with Russian-made RD-180 engines. When it finally reaches Mars in a few months, MRO will begin a series of 514 aerobraking maneuvers, where it skims through the top of the atmosphere to slow down its velocity and bring it into its final science orbit.

During its recent flyby of Mimas, Cassini found the Saturnian moon to be heavily battered and bruised by impact craters; it's the most heavily bombarded of Saturn's moons. It also got a perfect image of Mimas' Hershel crater, which is 140 km (87 miles) across, and makes the moon look like the Death Star. By analyzing the impact craters, scientists hope to calculate how many impacting asteroids moved through the region early in the life of our Solar System.

Earth isn't the only place that gets the Northern and Southern Lights, or auroras. NASA's Cassini spacecraft has taken an ultraviolet image of Saturn that shows its southern pole covered by an aurora. In this false-colour image, the blue indicates the aurora emissions created by hydrogen gas excited by electron bombardment, and the red-orange is reflected sunlight. Another photo, taken just an hour later shows how quickly these auroras are changing.

The MARSIS radar instrument on board Mars Express is now extended and fully operational, and ESA scientists have begun using it to probe beneath the surface of Mars in search of water and ice. During this initial commissioning phase, operators have used the instrument to examine Mars' topography to compare its reading against previous readings of the Red Planet to make sure its calibrated correctly. Within a few weeks they'll start isolating areas where the radar is penetrating beneath the surface to start mapping out underground layers.

Skywatchers in the Southeastern United States will have an opportunity to watch the International Space Station and the space shuttle Discovery fly overhead on Saturday morning at 5:50 am CDT.. Discovery will have undocked from the station three hours previously, so the two objects will be separated visually by about the width of the Moon. As a special bonus, the two spacecraft will pass close to the planet Mars as well.

NASA astronauts on board Discovery and the International Space Station held a tribute to remember the crew of Columbia, which was destroyed during its re-entry more than two years ago. Each crewmember wore a red shirt with Columbia's STS-107 mission patch, and spoke, paying their respects to the crew of STS-107, as well as Challenger, Apollo 1, Soyuz 1 and 11.

NASA has given the space shuttle Discovery a green light to return to Earth on Monday, August 8th. The agency's Mission Management Team has decided that the shuttle's heat shield and other systems are in good shape, after Wednesday's spacewalk to remove excess gap filler between shuttle tiles. The team also decided that a torn thermal blanket won't be a risk as the shuttle re-enters the atmosphere.

At least three massive asteroids smashed into the Earth more than 3.2 billion years ago, and caused such destruction, they dramatically changed the structure and composition of the Earth's surface. This is according to new research from scientists at the Australian National University. The team uncovered evidence of major earthquakes, faulting, and volcanic eruptions that were so violent they dramatically changed the way the Earth's surface was forming. This happened during a period that the Moon also suffered heavy bombardment.

Ahhh, summer time and the livin' is light and easy. Per chance there's an opportunity to escape the textbooks, computer screens and chores to engage in a more leisurely pursuit. Alex Brett offers a busy little mystery in her book, Cold Dark Matter. In it, a private investigator takes on the puzzle of an apparent murder at the FrancoCanadian telescope in Hawaii. A quick pace and twisting plot make this a fine read for those astronomy buffs who care to branch out a bit.

The Hubble Space Telescope spent 40 hours gazing at the same spot in the sky to produce a photograph filled with galaxies. The field shown in this image is a fraction of the size of the full moon in the sky, but it shows a rich diversity of galaxies. Some are big; some small; a few close; and most far away. The photograph was actually a bonus, taken in September 2003 while Hubble was using its other instruments for research in the same area.

NASA's Cassini spacecraft made a relatively close flyby of Saturn's moon Mimas on August 2nd, 2005. The 130 km (80 mile) crater Herschel makes the moon look amazingly similar to the Death Star from the Star Wars series of movies. Cassini passed only 62,700 km (38,800 miles) above Mimas; the closest it's ever been to the moon.

Astronaut Steve Robinson successfully pulled out the protruding gap fillers from between the shuttle's thermal protection tiles during his 7 hour spacewalk yesterday. The gap fillers came out with a simple tug; Robinson didn't need the makeshift hacksaw he'd brought with him. NASA officials were worried that the Nextel fabric could lead to overheating in the area during Discovery's re-entry. The filler material keeps the shuttle's heat tiles from bumping into each other during launch, but aren't necessary during landing.

NASA's Spitzer Space Telescope has peered through walls of galactic dust to spot supermassive black holes called quasars. Some quasars are visible to telescopes, but others are behind so much gas and dust they can only be seen in the infrared spectrum, which is good for viewing through dust. Based on background X-ray radiation, astronomers had an estimate for how many quasars are out there, but they could never see them with telescopes. Now Spitzer has shown that those quasars are there, just hidden.

With new instruments, astronomers are filling in all the pieces that help to explain how planets form out of extended disks of gas and dust around newborn stars. This process seems to happen quickly, often just a few million years is all it takes to go from dust to planets. But astronomers have found one proto-planetary disk that refuses to grow up. It's 25 million years old, and still hasn't made the transition to form planets. Lee Hartmann is with the Harvard-Smithsonian Center for Astrophysics, and the lead author on the paper announcing the find.

Astronauts Steve Robinson and Soichi Noguchi made their preparations to head outside the space shuttle Discovery today. This spacewalk had been planned for the mission, but shuttle managers gave the two men the additional task of fixing two protruding gap fillers in between the heat tiles on the underside of the shuttle. Robinson will attempt to pull the excess material out by hand, or use a hacksaw if that doesn't work.